JP2005143266A - Three-phase induction motor driving method and driving device used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that a star-delta system of is a two-step start is unapplicable to various loads, that a thyristor system is mainly of an analog system, and is unapplicable to such loads as require a large current at an initial stage, and that a frequency control system has a bad effect on a power supply in a factory because of the generation of the harmonic waves. <P>SOLUTION: A three-phase induction motor is started or stopped by a three-phase AC power supply, the phase control of which is performed by a semiconductor switch of an IGBT or an IEGT. At the time of rated rotation of the three-phase induction motor, the rated operation of the three-phase induction motor is performed by the three-phase AC power supplied from a bypass circuit that bypasses the semiconductor switch. The phase control of the three-phase AC input power supply is performed by the switching control of the IGBT or the IEGT with a CPU. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a driving method of a three-phase induction motor (motor) used for driving devices (electric loads) such as a blower, a pump, a refrigerator, an air conditioner, a conveyor, a pulverizer, and a robot, and a driving device used therefor. Slow start with the desired pattern at the start until reaching the rated operation, slow stop with the desired pattern at the stop after rated operation, and automatically stop the rotation of the three-phase induction motor when the input power supply or load abnormality occurs It is made to let you.

  Three-phase induction motors are widely used because they are relatively simple in structure, easy to handle, and inexpensive. There are various types of starting methods for the slow start, and the most basic one is a star delta type starting method. In addition, there are a phase control method using a thyristor, a frequency control method using an IGBT, and the like.

  In the star delta drive circuit, the stator winding of the three-phase induction motor is designed with a delta connection, and at the start, the stator winding is switched to the Y connection by a changeover switch to start the three-phase induction motor. When the rotation of the induction motor reaches the rated speed (rated rotation), the stator winding is switched to the delta connection so that the three-phase induction motor is driven.

  In the phase control type drive circuit, a three-phase power supply circuit and a three-phase induction motor are connected via a semiconductor switch, and the conduction angle of the semiconductor switch is actively controlled according to the load state, so that The induction motor starts and stops smoothly. There are various types of semiconductor switches used for this, but thyristors with antiparallel connection are often used.

  As one of the phase control type drive circuits, a bypass circuit is provided in parallel with the semiconductor switch. When starting and stopping the three-phase induction motor, the phase of the three-phase AC power supply is controlled by the semiconductor switch circuit to supply power to the three-phase induction motor. In some cases, a three-phase AC power source is fed to a three-phase induction motor through a bypass circuit that bypasses the semiconductor switch during rated rotation. In this case, the bypass circuit is provided with an electromagnetic switch, and the electromagnetic switch is provided with a sequence controller for opening and closing the switch. A sequence controller with a built-in microcomputer is known. When the three-phase induction motor is started and the rated rotation is started, the electromagnetic switch is opened with a timer, and when the rated rotation (rated operation) starts. The electromagnetic switch is closed to establish a bypass circuit, and at the same time, the semiconductor switch is designed to stop (see, for example, Patent Document 1).

JP 2000-201490 A

  The star delta type described above is a two-stage start and has a problem that it cannot cope with various loads. The above-mentioned thyristor method is mainly an analog type, and it cannot be applied to an S-shaped start-up, frequency fluctuation load, multi-step start-up, or a load that requires a large amount of current in the initial stage. There are challenges. The frequency control method described above has a problem that harmonics are generated, which adversely affects the power supply in the factory.

  In order to solve the problems of the respective driving methods described above, the present invention adopts a three-phase input power supply with phase control that does not easily generate harmonics, and considers cost reduction due to a future distribution amount in the phase control switching control element. Alternatively, real-time digital control is performed using a CPU in order to respond to various requests on the load side using IEGT. More specifically, it is as follows.

  The driving method of the three-phase induction motor of the present invention starts and stops the three-phase induction motor with a three-phase AC power source controlled in phase by a semiconductor switch by IGBT or IEGT, and bypasses the semiconductor switch at the rated rotation of the three-phase induction motor The three-phase induction motor is rated-operated with a three-phase AC power supplied from the bypass circuit, and the phase control of the three-phase AC input power is performed by switching control of the IGBT or IEGT by the CPU. In addition, after the transition to rated operation at the start of the three-phase induction motor and before the transition from rated operation to stop, the three-phase induction motor is operated with a phase-controlled three-phase AC power source and a bypass circuit. In parallel with the operation with the three-phase AC power supplied from By controlling the conduction time of IGBT or IEGT to control the output voltage of the three-phase AC power applied to the three-phase induction motor, the start pattern and the stop pattern of the three-phase induction motor can be set. Detects abnormalities such as voltage levels of three-phase AC input power supply and three-phase AC output power supply, phase loss of two or more phases, frequency range, output current over, etc., and power supply to the three-phase induction motor is detected when an abnormality is detected. The three-phase induction motor is automatically shut off and automatically stopped.

  The driving device for a three-phase induction motor according to the present invention includes an input phase detection circuit 1 that detects the phase of an input three-phase AC power supply, an IGBT or IEGT that controls the phase of the three-phase AC power supply, and a switching control of the IGBT or IEGT. Switching control circuit 2, bypass circuit 3 for bypassing IGBT or IEGT and supplying three-phase AC power to a three-phase induction motor, electromagnetic switch 4 for turning on / off bypass circuit 3, and controlling on / off of electromagnetic switch 4 The input / output control circuit 5 for controlling the input of the input unit 6 such as a keyboard for inputting the start / stop pattern of the three-phase induction motor (IM) and the other setting items and the input unit 6 Display 8 for displaying numerical values and other contents, display control circuit 9 for controlling display of display 8, output power from IGBT or IEGT An output phase detection circuit 10 for detecting the phase, an output current detector 11 for detecting the current of the output power supply, the switching control circuit 2 and the switch control circuit based on signals from these circuits, preset conditions, etc. A central processing circuit 11 that performs control of 5 and the like, an alarm 12 that notifies an abnormality alarm when an abnormality is detected, and the like are provided.

The driving method of the three-phase induction motor of the present invention has the following effects.
1. Since the switching of the IGBT or IEGT is controlled by the CPU, the IGBT or IEGT can be controlled in accordance with the desired start and stop conditions, and the three-phase induction motor can be driven in accordance with the start and stop conditions of the load. Can do.
2. When the three-phase induction motor is started and stopped, the power source temporarily controlled by the IGBT or IEGT1 and the input power source from the bypass circuit are driven in parallel, so that the operation at the start and stop is smooth.
3. If an abnormality occurs in the three-phase AC power supply during rated operation of the three-phase induction motor, the power supply to the three-phase induction motor is cut off and the three-phase induction motor is stopped, so that the three-phase induction motor is not overwhelmed.
4). Due to the characteristics of the IGBT or IEGT1, since the switching speed is fast, it is possible to follow a slight voltage change and fine phase control is possible.
5). Since the switching loss is small due to the characteristics of the IGBT or IEGT1, it is possible to save power. Further, during rated operation, operation is performed by a bypass magnet, and since IGBT or IEGT is not used, heat generation is small and power is saved.
6). Due to the characteristics of IGBT or IEGT1, switching is turned off only by a drop in the gate voltage, so that a protection circuit is not required and the circuit configuration is simplified.
7). When IEGT is used, there are the following effects in addition to the above effects. In other words, by devising the element structure on the emitter side, electron injection is promoted, the on-voltage characteristics are as low as GTO, and it is easy to drive and has a high shut-off capability like IGBTs.
8). Since the phase control of the three-phase input power supply is performed by IGBT or IEGT, there is little adverse effect on the power supply due to harmonics as in the case of frequency control.
9. Since the driving method of the present invention is a digital control method, it has many advantages as compared with the analog control method.
(1) Since there are few errors in the setting values of the starting voltage and starting current and detailed setting is possible, when using multiple units at one place, all starting styles can be obtained as set, and the reliability from customers is high. high.
(2) Since the starting style can be set in various patterns according to the load, smooth starting can be performed even under heavy loads, and the application range is wide.
(3) Since the number of parts constituting the drive device is small, there are few failures, and even if there is a failure, it is easy to determine what is the cause by the log fill etc. of the CPU, so that maintenance is easy.

The drive device for a three-phase induction motor of the present invention has the following effects.
1. An IGBT or IEGT that controls the phase of the three-phase AC power supply and a switching control circuit that controls the switching of the IGBT or IEGT are provided, and these controls are performed digitally by the CPU, so that detailed control according to the state of the load can be performed.
2. A bypass circuit that bypasses IGBT or IEGT and supplies three-phase AC power to a three-phase induction motor, an electromagnetic switch that turns ON / OFF the bypass circuit 3, and a switch control circuit that controls ON / OFF of the electromagnetic switch 4 Since it is provided, the parallel operation can be performed easily and reliably.
3. Three-phase induction motor (IM) start / stop pattern, input unit such as a keyboard for inputting other setting items, display unit for displaying input numerical values and other contents, and display for controlling the display of the display unit Since it is equipped with a control circuit, it is easy to set conditions and make detailed settings.
4). An input phase detection circuit for detecting the phase of the input three-phase AC power supply, an output phase detection circuit for detecting the phase of the output power supply from the IGBT or IEGT, an output current detector for detecting the current of the output power supply, etc. Therefore, the abnormality can be detected quickly and reliably, and the three-phase induction motor (IM) can be quickly stopped when the abnormality occurs, so there is almost no damage to the three-phase induction motor and the load.
5). Since an alarm or the like for notifying an abnormality alarm is provided when an abnormality is detected, it is possible to know the abnormality quickly and surely, and it is possible to quickly handle the abnormality process.
6). Even if the control voltage is turned off when an abnormality is detected, the abnormal state is held by the non-volatile storage device, and since the release is only a reset input, the abnormality process can be performed reliably.

  An example of an embodiment of a driving method and a driving apparatus for a three-phase induction motor according to the present invention will be described with reference to FIGS. In FIG. 1, a three-phase induction motor IM, an input phase detection circuit 1 that detects the phase of an input three-phase AC power source, an IGBT or IEGT that controls the phase of the three-phase AC power source (hereinafter collectively referred to as IGBT) .), Switching control circuit 2 for controlling the switching of the IGBT, bypass circuit 3 for bypassing the IGBT to supply a three-phase power supply to the three-phase induction motor, an electromagnetic switch 4 for turning on / off the bypass circuit 3, an electromagnetic switch 4 Switch control circuit 5 that controls ON / OFF of the input, input / output unit 6 such as a keyboard for inputting start / stop patterns of the three-phase induction motor IM and other setting items, and an input control circuit that controls input of the input unit 6 7. Display 8 such as a liquid crystal screen for displaying the input numerical value, error, operation state, etc., display control circuit 9 for controlling the display of the display 8, IGBT or Is an output phase detection circuit 10 for detecting the phase of the output power supply from the IEGT, an output current detector 11 for detecting the current of the output power supply, the switching control based on signals from these circuits, preset conditions, etc. Central processing unit CPU for controlling circuit 2 and switch control circuit 5, etc., buzzer for notifying abnormality alarm when abnormality is detected, speaker 12, light and other alarming device 12, start / stop switch 13, error reset switch 14, input / output A circuit 15 and a nonvolatile storage circuit 16 for storing input conditions, detection values, and the like are provided. The drive device of the present invention can include other devices, and in some cases, unnecessary ones can be eliminated.

  The IGBT (Insulated Gate Bipoolar Trasistor) or IEGT (Injection Enhanced Gate Transistor) is inserted in series between the three-phase AC power source and the three-phase induction motor IM. One is inserted in each of the phase, the S phase, and the T phase. The IGBT is turned on when an ON signal is input to the gate, and then the IGBT is also turned OFF when the gate signal is turned OFF.

  The IGBT in FIG. 1 is provided with an IGBT protection circuit, for example, a thermal relay for temperature management, and the electromagnetic relay 4 is provided with a thermal switch for load protection.

  The drive device for the three-phase induction motor shown in FIG. 1 is one in which the three-phase induction motor IM is slow-started with the start pattern of FIG. 2, for example, and is slow-stopped with the stop pattern of FIG. In addition, for a short time after rated operation at the time of starting, for example, about 1 to 30 seconds and for a short time before shifting from rated operation to stop, for example, about 1 to 30 seconds, the three-phase input power supply is IGBT. The phase control power source that is phase-controlled and the bypass power source that bypasses the IGBT through the bypass circuit and supplies the three-phase induction motor to the three-phase induction motor are operated in parallel. In addition, if the motor is driven with a too low three-phase input voltage, the motor may be burned out. Therefore, the offset voltage V1 is set as shown in FIG. 2 so that the motor is not driven at a voltage lower than that. Since the offset voltage V1 varies depending on the load, it can be set in accordance with the load.

In order to realize the slow start and slow stop, the driving apparatus of FIG. 1 can set the driving conditions (starting pattern, stopping pattern) by selecting the voltage v and the time t. For example, if the target point (voltage v, time t) of the start pattern and the target point (voltage v, time t) of the stop pattern are set to 10 points and the voltage v and time t of these 10 points are selected, there are 10 levels. A start pattern and a stop pattern can be set. FIG. 3 shows voltage V ₁ (30% output) during time t ₁ , voltage V ₂ (60% output) during time t ₂ , and voltage V ₃ (100% output) during time t _3. This is an example of setting. The number of target points, the values of voltage v, and time t can be arbitrarily set according to the load state and specifications.

  In the present invention, other desired items can be set. For example, the magnet operation time of an auto test (repeated test) for performing self-diagnosis of the device can be set between 1 and 999 seconds, or the complete off time can be set between 5 and 999 seconds. . These settings can be made by inputting from the keyboard 6 while viewing the liquid crystal screen (LCD). The set time may be a numerical value other than the above numerical values.

The CPU program is divided into several modules. Each program runs independently and contacts each other when needed. For example, the following modules are prepared.
1. Main module 2. LCD (liquid crystal) control module 3. Backup ROM control module 4. Keyboard control module I / O control module 6. Motor control module Error detection module 8. IGBT control module 9. Slow start / stop slope control module The modules 1 to 9 described above are positioned as shown in Fig. 8. Basically, the lower module cannot communicate with the main module, and the main module is always connected to the lower module. Checking the operating status.

Error detection can be performed in the drive device of FIG. In FIG. 1, the following types of monitoring are always performed so that errors can be detected.
1. Input voltage φ
2. Open phase more than phase 2. Frequency range Input reverse phase 5. Each phase open phase (λ output)
6). Output current over

In the drive device of FIG. 1, the phase of the three-phase input power supply is detected as follows to generate an IGBT control signal.
(1) The input phase detection circuit 1 in FIG. 1 takes out the timing of the zero cross point of the sine wave (three-phase input power source) in FIG. 4 (a) as shown in FIG. 4 (b) and detects its frequency and period T. To do. When a half cycle T is output in a time-sharing manner, an output voltage is obtained.
(2) When a voltage of 30% of the sine wave of FIG. 4A (30% in terms of the area of the sine wave) is output, the time from the zero cross point to the next zero cross point (FIG. 4C) ( When the IGBT is turned on only for a period of 30% of the area ratio of the period T), the output voltage becomes 30%.
(3) When outputting a voltage of 60% of the sine wave of FIG. 4A (60% in terms of the area of the sine wave), the time between the zero cross point and the next zero cross point as shown in FIG. When the IGBT is turned on only for the time of the area ratio of 60%, the output voltage becomes 60%.
(4) As described above, the start pattern and the stop pattern can be set (slope control) as shown in FIG. 2 by setting the IGBT ON time by the number of set target points. Therefore, any slope can be set if the target point is given by voltage v (%) and time t. However, since the phase of the current is delayed from that of the voltage, when the IGBT is turned off at the point of the input voltage 0 (FIG. 5c, point A) in (FIGS. 5a, b), the output current value is large (FIG. 5c). Since the IGBT is turned off (FIGS. 5c and d), a large reverse current is output, and as shown in FIG. 5F, the output voltage and current are monitored and AND is performed, and the output current becomes zero. (The time t _{x in} FIG. 5) is waited until the IGBT is automatically turned off (the IGBT is controlled).

  In the drive device of FIG. 1, the phases of the input three-phase AC power source and the output three-phase AC power source output from the IGBT are detected. As shown in FIG. 6A, the phases of the input three-phase AC power supplies U, V, and W are shifted by 60 degrees. When the zero cross point of this input three-phase AC power supply is detected, the result is as shown in FIG. In the normal phase, the detection signal of the zero cross point is in the order of 1-2-3 in FIG. When this is in the order of 1-3-2, the phase is reversed, and in the case of 1-3-1, it can be determined that the V phase is a missing phase. There are other patterns of phase failure.

In the driving apparatus shown in FIG. 1, when the power switch (start switch) 13 is turned ON, the self-check is performed as follows (for example, as shown in FIG. 7).
1. The backup data of the storage circuit 16 in FIG. 1 is read, and the presence / absence of an unprocessed error (whether an abnormality remains) is confirmed in the unprocessed error step of FIG.
2. If there is an unprocessed error, the process waits for error processing, and the error processing step is YES. Here, error processing is artificially performed, and when the error reset switch 14 of FIG. 1 is turned ON, backup writing is automatically updated.
3. When the backup data is read again and there is no unprocessed error in the unprocessed error step, the start pattern and stop pattern settings are checked in the next setting check (FIG. 7) step. When the setting check results in an error, the setting initialization is confirmed, and when it becomes OK, a new setting is made artificially.
4). After the setting, when the setting check is performed again and the result is OK, the process proceeds to the setting mode (FIG. 7) step. Here, when the setting needs to be changed, YES, and when it is not necessary to change, NO. If YES, set manually.
5). If the setting mode step is NO (setting change not required), the process proceeds to the test mode (FIG. 7) step to ask whether or not to perform self-diagnosis of the drive device. Here, in the case of YES, the process shifts to a test routine and a repeated test (self-diagnosis) of the drive device is automatically performed. If NO at the test end step, the test is continued or restarted until the stop switch 13 is turned on. If YES, return to the first step of reading backup data.
6). If the test mode step is NO, the process proceeds to the command wait or error detection step (FIG. 7). If an error is detected in this step, registration in the storage circuit 16 (FIG. 1) is required for backup registration, and the process proceeds to the error processing step, where it is processed in the same manner as in the error processing described above. When a command is issued in the command wait or error detection step, the command waits for the start switch 13 (FIG. 1) to be pressed. In this case, even after the operation of the driving device of FIG. 1 is started, the program is in a command waiting state. When the stop switch 13 (FIG. 1) is pressed in this state, the operation of the driving device of FIG. Is stopped.

In the above operation, the operation of the driving device in FIG. 1 when the start switch is pressed is as follows.
1. When a three-phase AC power supply is applied in a state where a control voltage is applied to the CPU, the input phase detection circuit 1 checks whether the three-phase AC voltage is missing or reversed.
2. Here, when the start switch 13 is turned on, if all the contents to be set in the memory circuit 16 have been completed, the operation of all the circuits starts.
3. If the contents to be set are not stored in the storage circuit 16, the storage circuit 16 is provided (set) with the keyboard 6 via the input control circuit 7 according to the contents displayed on the liquid crystal display.
4). If there is no abnormality in the input / output voltage current, the IGBT control circuit generates a gate pulse according to the setting.
5). When a voltage is applied to the output side by the generated gate pulse, the output phase detection circuit 10 and the output current detection circuit 11 start detecting abnormality of the output voltage, and if there is a reverse phase, open phase, overcurrent, etc., the CPU To inform.
6). If no abnormality is detected, the IGBT starts phase control by the gate pulse, and the IGBT shifts to 100% full output (rated operation) according to the start curve set. Thereafter, the electromagnetic switch 4 is driven by the magnet control circuit 5 according to the setting, and a parallel operation state in which both the phase-controlled power supply and the bypass power supply are operated is set.
7). The parallel operation is automatically completed after a predetermined time (several seconds) according to the setting, the IGBT control circuit 2 sets the gate pulse to zero, the IGBT is turned off, and the three-phase induction motor is operated independently by the bypass power source.
8). When the stop switch 13 is pressed to stop the three-phase induction motor during the single operation with the bypass power source, the IGBT control circuit 2 starts 100% output according to the setting of the input / output circuit 15 and enters the parallel operation. Then, after a predetermined time has passed (several seconds later), the parallel operation ends, the magnet control circuit 5 turns off the electromagnetic switch 4, the supply of bypass power to the three-phase induction motor is shut off, and the phase is controlled by the IGBT. Shift to stand-alone operation according to the stop curve.
9. Thereafter, according to the setting, the IGBT control circuit 2 sequentially turns the gate pulse of the IGBT from 100% to 0%, and the rotation of the three-phase induction motor stops.
10. In the drive device of FIG. 1, if there is an abnormality in the input phase detection, output phase detection, or output current detection, the control power is turned off until the CPU stops the rotation of the three-phase induction motor and the error reset switch 14 is pressed. However, the three-phase induction motor is not rotated by retaining the contents of the error storage circuit.
11. All the control is performed by the CPU.

The schematic of the drive device of the three-phase induction motor of the present invention. Operation | movement explanatory drawing of the drive method of the three-phase induction motor of this invention. FIG. 3 is an explanatory diagram for setting a start pattern in the method for driving a three-phase induction motor of the present invention. (A) is an input voltage waveform explanatory diagram, (b) is a waveform explanatory diagram of the zero cross timing of the input voltage, (c) a waveform explanatory diagram of an IGBT control signal when the voltage is 30%, and (d) is when the voltage is 60%. The waveform explanatory drawing of IGBT control signal of. (A) is an input voltage waveform explanatory diagram, (b) is an input voltage zero cross waveform explanatory diagram, (c) an IGBT control signal waveform explanatory diagram, (d) an output current waveform explanatory diagram, (e) an output current zero cross waveform explanatory diagram, (F) AND circuit explanatory drawing for obtaining the control signal which turns off IGBT. (A) is waveform explanatory drawing of the input voltage in this invention, (b) is phase detection explanatory drawing of the zero crossing point of the waveform of (a). FIG. 2 is a flow explanatory diagram of a self-check of the drive device of FIG. 1 when the start switch of FIG. 1 is turned on. The positional relationship explanatory view of various modules.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input phase detection circuit 2 Switching control circuit 3 Bypass circuit 4 Electromagnetic switch 5 Switch control circuit 6 Input part 7 Input control circuit 8 Display 9 Display control circuit 10 Output phase detection circuit 11 Output current detector 12 Alarm 13 Start / Stop switch 14 Error reset switch 15 Input / output circuit 16 Memory circuit

Claims (5)

  The three-phase induction motor is started and stopped with a three-phase AC power source that is phase-controlled by a semiconductor switch by IGBT or IEGT. At the rated rotation of the three-phase induction motor, a three-phase AC power source supplied from a bypass circuit that bypasses the semiconductor switch A driving method for a three-phase induction motor, characterized in that a three-phase induction motor is rated and the phase of the three-phase AC input power is controlled by switching control of the IGBT or IEGT by a CPU.   The method for driving a three-phase induction motor according to claim 1, wherein the phase of the three-phase induction motor is temporarily controlled after the transition to the rated operation at the start of the three-phase induction motor and before the transition from the rated operation to the stop. A driving method for a three-phase induction motor, characterized in that the operation with a three-phase AC power source and the operation with a three-phase AC power source supplied from a bypass circuit are parallel.   3. The method of driving a three-phase induction motor according to claim 1 or 2, wherein the three-phase AC power supply voltage applied to the three-phase induction motor is controlled by controlling the conduction time of the IGBT or IEGT to control the three-phase induction motor. A method for driving a three-phase induction motor, characterized in that a start pattern and a stop pattern of the induction motor can be set.   The method for driving a three-phase induction motor according to any one of claims 1 to 3, wherein the voltage levels of the three-phase AC input power source and the three-phase AC output power source, the phase loss of two or more phases, the frequency range, and the output current over The drive of a three-phase induction motor is characterized in that when an abnormality is detected, the power supply to the three-phase induction motor is automatically shut off and the three-phase induction motor automatically stops. Method.   Input phase detection circuit (1) for detecting the phase of the input three-phase AC power supply, IGBT or IEGT for phase control of the three-phase AC power supply, switching control circuit (2) for switching control of the IGBT or IEGT, IGBT or IEGT Bypass circuit (3) for supplying three-phase AC power to the three-phase induction motor by bypassing, electromagnetic switch (4) for turning ON / OFF the bypass circuit (3), and ON / OFF control for the electromagnetic switch (4) Switch control circuit (5), input unit (6) such as a keyboard for inputting the start / stop pattern of the three-phase induction motor (IM) and other setting items, and input control for controlling the input of the input unit (6) Circuit (7), display unit (8) for displaying input numerical value, error, operation state, etc., display control circuit (9) for controlling display of display unit (8), IGBT or IEG The output phase detection circuit (10) for detecting the phase of the output power supply from the output current detector (11) for detecting the current of the output power supply, the signal from these circuits, preset conditions, etc. Three-phase characterized by comprising a central processing circuit (11) for controlling the switching control circuit (2), switch control circuit (5), etc., an alarm (12) for notifying an abnormal alarm when an abnormality is detected, etc. Induction motor drive device.

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